Drills, especially, a drill formed of cemented carbide that is more brittle than high-speed steel is subjected to edge tip treatment to reinforce a cutting edge for longer life.
The cutting edge can be reinforced by removing a sharp portion of t e edge tip, for example by chamfering or honing.
In edge tip treatment for reinforcement described in, for example, PTL 1 below, a cutting edge of a twist drill is chamfered to be a combination of a straight face and a curved face or to be a curved face. The curved part of the chamfered portion is mirror-finished or satin-finished to suppress floating of hard particles on the surface of the curved part.